My youngest son was an escape artist. At 1 1/2 years old one morning while the wife was asleep and I was at work; he climbed out of his crib, opened his bedroom door, wend downstairs, climbed over a dog gate, opened the dead bolt for the back door in the kitchen, then ran down the front driveway in his pj's just as her mother was pulling up...
We had installed a new door on his room and hadn't put the new door knob on. So we left the knob off still, and added a hook and latch to lock it from the outside to keep him in....